biochem 2 english

• What must a cell complete to divide?

  The cell must grow, copy its genetic material, and physically split into two daughter cells.
• Why is the cell cycle considered a cycle?

  Because the two daughter cells can start the same process over again from the beginning.
• What are the two major phases of the cell cycle in eukaryotic cells?

  Interphase and the mitotic (M) phase.

  
• What is the longest phase of the cell cycle?

  Interphase is the longest phase of the cell cycle.
• What is the highest degree of DNA compaction?

  Chromosome structure is the highest degree of DNA compaction.

  
• What are the stages of interphase in the cell cycle?

  • G1 growth phase: Cell grows, makes proteins and organelles.
  • S synthesis phase: Cell synthesizes a complete copy of DNA and duplicates centrosomes.
  • G2 growth phase: Quality control of DNA integrity and preparation for mitosis.

  
• What occurs during the S phase of interphase?

  The cell synthesizes a complete copy of the DNA in its nucleus and duplicates the centrosome.
• What is the role of centrosomes during the M phase?

  Centrosomes help separate DNA during the M phase.
• What happens during the G2 phase of interphase?

  The cell checks the integrity of the DNA and prepares for mitosis.

  
• How do chromosomes appear during interphase?

  Chromosomes appear dispersed during interphase.
• What is euchromatin and heterochromatin?

  Euchromatin is less condensed and transcriptionally active, while heterochromatin is more condensed and transcriptionally inactive.
• What are DNA and RNA made of?

  DNA and RNA are made up of monomers known as nucleotides.
• What is a polynucleotide?

  A polynucleotide is a chain formed when nucleotides combine.
• What are the three parts of a nucleotide?

  A nucleotide consists of a nitrogenous base, a five-carbon sugar, and at least one phosphate group.

  
• How is the sugar molecule positioned in a nucleotide?

  The sugar molecule has a central position with the base attached to one carbon and the phosphate group attached to another.

  
• What are the fundamental organizational units of chromatin?

  • Nucleosomes are the fundamental units.
  • Chromatin is a double-stranded helical structure of DNA.
  • DNA is complexed with histones to form nucleosomes.

  
• What is a nucleosome composed of?

  A nucleosome consists of eight histone proteins around which DNA wraps 1.65 times.

  
• What is chromatin composed of?

  Chromatin contains protein and DNA in equal proportions, along with a small amount of RNA.

  
• What role do histones play in DNA packaging?

  Histones package and order the DNA into structural units called nucleosomes.

  
• How many major classes of histones are there in eukaryotic cells?

  There are five major classes of histones in eukaryotic cells.
• What is supercoiling in DNA?

  Supercoiling occurs when the axis of the DNA double helix is coiled on itself.

  
• What facilitates the separation of DNA strands required for replication and transcription?

  Supercoiling facilitates the separation of DNA strands.

  
• What are topoisomerases?

  Topoisomerases are nuclear enzymes that play essential roles in DNA replication, transcription, chromosome segregation, and recombination.
• What is the function of Type I topoisomerase?

  Type I topoisomerase transiently breaks one of the two DNA strands.
• What is the function of Type II topoisomerase?

  Type II topoisomerase breaks both DNA strands.
• What is the primary structure of nucleic acids?

  • The sequence of nucleotide bases.
  • The way these bases are covalently bonded to each other.

  
• What is the secondary structure of DNA?

  • Consists of two polynucleotide chains.
  • Wrapped around one another to form a double helix.
  • Regular, stable structure taken up by the nucleotides.

  
• Who was Chargaff and what did he discover?

  Chargaff discovered that base composition changes from one species to another and that A = T and C = G.
• What is the structure of DNA?

  DNA is a right-handed double helix made of deoxyribose and phosphate groups.

  
• How are DNA strands oriented in the double helix?

  DNA strands are antiparallel in the double helix.
• What holds the double helix of DNA together?

  The double helix is held together by hydrogen bonding between complementary base pairs.
• What is denaturation of DNA?

  Denaturation is the process where the double helix is disrupted due to pH extremes or high temperatures.

  
• What is the annealing process in DNA?

  Annealing is the process by which two strands spontaneously rewind when temperature or pH returns to normal.

  
• What are the steps involved in the annealing process of DNA?

  1. Two strands spontaneously rewind.
  2. Occurs when temperature or pH returns to normal.